The presentation of evidence at trial begins when the attorney for the "plaintiff" (the person suing) begins calling witnesses. The plaintiff's attorney does the initial questioning of the witness, which is called direct examination. The purpose of a direct examination is to get the witness to testify about facts that support the plaintiff's case.
During direct exams, attorneys can ask witnesses to identify demonstrative evidence, such as documents and photographs and/or to explain what they saw, heard, or did in relation to the case at hand. For example, a plaintiff's attorney in a car accident personal injury lawsuit may call a bystander to testify as to what he or she saw just before, during, and/or after the accident, including what the weather was like, what happened during the accident, and any other details the witness remembers from the day.
During direct examination, a judge will have some control over the scope and form of the questions. The judge can stop repetitive questioning and prevent a lawyer from asking leading questions, which imply, suggest, or prompt the witness to give a particular answer. However, a judge won't restrict questions unless the other attorney makes an objection. If the plaintiff's attorney is leading the witness, then the attorney for the "defendant" (the person being sued) can object to the question. After listening to the objection, the judge with either sustain (grant) or overrule (deny) it and allow the witness to answer the question.
Generally, a witness can't give an opinion or draw conclusions from the evidence unless that person has been qualified as an expert witness. For example, the bystander to the accident won't be allowed to provide an opinion as to what caused the accident or what medical damages the plaintiff sustained—only an accident reconstruction specialist or a medical expert can provide opinions on those topics.
After the plaintiff's attorney completes the direct examination, the defendant's attorney gets to cross-examine the witness. Cross-examination is a fundamental right in the American system of justice. Generally, cross-examination is limited to matters covered during the direct examination. The attorney may ask leading questions during cross-examination.
Challenging Witness's Credibility on Cross-Examination
During cross-examination, the attorney tries to undermine or impeach the witness's credibility by showing that the witness is not reliable or that the witness may have misstated something or even lied during the direct examination. For example, if the witness said one thing in an accident report or during a deposition and then testified differently at trial, the defendant's attorney can refer to the previous statements and show inconsistencies in the story.
The attorney might also try to show that the witness is biased or prejudiced toward a party in the case. Another way to undermine the witness's credibility is to show that the witness has a stake in the outcome of the case, which might influence the testimony. The attorney can also question the witness about any felony criminal convictions or about any crimes involving dishonesty. Just as on direct examination, the opposing party's attorney can raise objections to the questions posed. The judge then rules on the objection.
Redirect and Recross Examination
Following cross-examination of the witness, the plaintiff's attorney has an opportunity to ask the witness follow-up questions regarding topics discussed during the cross. After this, the opposing attorney can conduct a final recross examination of the witness, which is limited to the subjects brought up during the redirect.
Once the plaintiff's attorney has called all of the plaintiff's witnesses, the defendant's attorney begins calling witnesses. The same procedure is followed as in the plaintiff's presentation of witnesses. The defendant's attorney conducts direct examination of the witnesses, and the plaintiff's attorney will conduct cross-examinations.